His deteriorating health is a major factor in discussions over his participation however. Ali has Parkinson's disease, and while he is well enough to have travelled to London for a series of charity engagements this week, it remains to be seen what part he will play.

Reports suggest he will lead a parade of great athletes but discussions are ongoing. Sources said it was unlikely he would be asked to light the Olympic cauldron, a role he fulfilled in Atlanta in 1996, but he seems certain to appear.

Final rehearsals for the ceremony are under way this week, with the last full run-through scheduled for Wednesday evening.

Around 40,000 people watched a rehearsal on Monday, with reaction on social media overwhelmingly positive about what they had seen.